Telephone system



1944- A. CHRISTIAN EI'AL 2,339,376

TELEPHONIEISY'STEMI Filed July 10, 1941 2 Sheets-Sheet l A 7b/9AX.

. I mvsrv'rons DAVID ADAM CHRISTIAN BERNARD ANTHONY HENSLER av Z? Z i 4 D. CHRISTIAN ETAL ,339,376

TELEPHONE SYSTEM 2 Sheets-Sheet" 2 Filed Jui 10. 1941 INVENTORS DAVID ADAM CHRISTIAN BERNARD ANTHONY HENSLER ATTORNEY Patented Jan. 18, 1944 TELEPHONE SYSTEM David Adam Christian and Bernard Anthony Hensler, London, England, assignors to Siemens Brothers & Co. Limited, Westminster, London, England, a British company Application July 10, 1941, Serial No. 401,716 In Great Britain August 12 1940 20 Claims.

This invention relates to automatic telephone systems and is particularly concerned with improved arrangements whereby a privileged subscriber may obtain direct access to certain other subscribers with whom he wishes frequently to communicate without passing over the usual switching apparatus of th exchange. The invention is especially applicable to private automatic exchanges with or without public service facilities.

Arrangements have previously been proposed in which a connection from a privileged subscriber to a wanted party may be set up and the wanted party called without the caller being required to remove hi receiver. Th present invention has in view improved arrangements of this kind.

In the present invention a call from a privileged subscriber to any one of a number of other subscribers to whom he is given privileged access facilities is set up and the wanted party called in response to a momentary operation of a key, and it is not necessary for the privileged caller to take any other action until he receives a signal indicating that the called party has answered. The connection is switched through when both subscribers have removed their receivers. If the called line is busy, a signal is given to the privileged caller and the connection may remain set up until the called line becomes free whereupon it is seized and the waiting connection switched through.

It is a feature of the present invention that while a privileged connection is in such a waiting condition, a privileged callers line is open to receive incoming calls without involving the release of the waiting connection. The waiting connection is, however, prevented from seizing the wanted line should this line become free before an incoming call has finished, but the facility of seizing the wanted line is restored when the incoming call finishes. If the caller does not wish to wait for a called line to become free. he may, by exercising a right-of-way facility enter the existing connection, or he may simply cancel the call by the momentary operation of a cancelling key. The invention also provides means whereby a privileged subscriber may set up a second call merely by operating the key relevant to the party required, the ensuing action resulting in the release of the earlier connection.

A specific embodiment of the invention will. now be described by way of example with refer ence to the accompanying drawings comprising Figs. 1 and 2. These show the circuits of a direct broadly known and form no part of the inven tion, they are not shown and will'not bedescribed but reference to them will be made where necessary.

It is assumed that a limited number of stations willbe able to receive calls over the direct access path and these stations besides their usual'connection to the P. A. X system will be connected in the banks of a connector in the direct access path. The connector is a single motion selfclrive stepping switch set by the marking method and is represented by its stepping magnet CDM and its wipers CIC5. The marking is effected by marking relays W, X, Y, Z operated by keys MK at the station of a subscriber who is given the privilege of direct access. The keys provide for 10 markings but if more than 10 stations are to be called directly, further keys would be provided wired in parallel with the appropriatekeys of the first decade but provided with an additional contact which closes a circuit for a relay V the effect of the operation of which is to change over the connection to the test wiper from wiper C4 to wiper C5. If, however, only 10 markings are provided for, the connection shown in dotted line over the back of contact 112 may be made permanent, or a strap may be provided which may be removed if the number of markings should exceed 10 at any time. 'The direct access path includes a feeding bridge with feed relay A on the incoming side and feed relay D on the outgoing side. Relays F and TR. are ring tripping relays and relays 'B, CO and S are slow re leasing relays. lAt'a privileged callers station his instrument is shown' diagrammatically at ET and the keys for direct calling are designated MK as before referred to. In addition'a key RWK is provided by means of which the caller can enter a busy connection. The condition of a called line is indicated by th lamp GL, indicative of a free line and RL indicative of a busy line.

To make a call over the P. A. X system, the caller removes his receiver at instrument ET and loops the line to the line circuit over contacts called line is busy, the privileged caller can if he wishes enter the line by depressing key RWK thereby extending earth over contacts Z213 and 1312 to wire RWL leading to the line circuit. This Wire is connected in a bank of the line finder in a position corresponding to the contacts connected to the privileged subscribers line, the associated Wiper being connected to a winding of the connector test relay which may thereby be operated to switch the connection through to the busy line. Arrangements of this kind are disclosed in British specification No. 355,927.

To call a stationdirectly, a. privileged caller presses the key appropriate to the wanted station and awaits a lamp indication of the state of the called line. If this is free, lamp GL glows and when the called party answers by removing his receiver, the callers bell is rung and he then removes his receiver and can commence his con.- versation immediately.

When one of the keys MK is pressed, earth is extended over contact 1713, rectifier MRC, the key contacts, one or more of the marking relays W, X, Y, Z, contacts [c4 and sl, to pilot relay BD. The marking relay or relays operate and lock up over their contacts I and contact cal and relay BD operates and holds over the locking circuit for the marking relays. The keys MK therefore may be of the non-locking type. On the operation of relay BD the following circuit is closed. for relay B; earth over contacts col, bdl, tb2, tr5, f1, relay B to battery. Contact bd2 earths the test wire in the callers line circuit to mark his line engaged in the P. A. X system. Relay B operates and at contact I)! prepares an alternative holding circuit for itself when relay BD releases. Contact 122 connects an operating earth for several of the relays, contact b3 prepares an alternative busy earth connection for the calling line to become effective on the release of relay BD, contacts b4 and b5 disconnect the callers speaking wires from the linecircuit and extend them to the direct access path, contact b6 prepares a locking circuit for relay CO and contact b1 prepares a circuit for the busy relay BL. An immediate result of the closure of contact b2 is the operation of start relay S. On its operation, contact s! opens one path in the operating circuit for relay BD but this relay is maintained over contact tb3, contact s2 disconnects the ringing circuit from the negative.

A contact in the bank of wiper C4 is marked by the battery connection over relays TA and TB and the pyramid of contacts of the marking relays and the connector magnet drives the wipers round in search of the marked contact, the magnet interrupting its own circuit at contact calm. It may here be mentioned that if a line having a direct call designation greater than 10 is called, relay V will be operated and locked in parallel with the marking relay or relays and test for the marked line will be made over wiper C5 and front contact '02, the strap shown in dotted lines having been removed from its back contact.

When the connector wipers reach the contacts of the marked line, relays TA and TB operate to earth over contact b2, contact ta! opening the magnet circuit to prevent further stepping and contact tbl disconnecting relay S and providing a holding circuit for relays TA and TB. Relay TA may be of the high speed type. Contact tb2 changes over in the circuit for relay B but as this relay is slow in releasing it does not release before contact bdl re-c1oses its circuit consequent on the quicker release of relay BD by the opening of contact tb3, relay S not yet having released. Consequent on the release of relay S which takes place after a short delay period, a circuit for the marking relays and relay BD is re-prepared at contact sl, a point in the circuit of the connector magnet is opened at contact s3 and a point in the marking circuit is opened at contact $4. The line is tested and if it is free test relay H operates from earth over contacts 122, ml and lets, the upper winding of the relay, wiper C3 to battery over the winding of the called partys out 01f relay. Relay H locks up over its lower winding and X contact hi, extends ringing current over wire IRl, winding (I) of relay TR, contacts s2, Z224, and W2 and 7L2, the return circuit being over contacts h3 and H3 and earths the outgoing test wire at contact 11.5 to mark the line engaged. Contact k5 .closes a circuit extending from earth over contact Z223, rectifier MRB, lamp GL, contacts M2 and 71.5, resistance to battery. Lamp GL glows to indicate to the caller that the line has been tested and found free. Meanwhile ringing current is applied to the called partys line over wire 1R5. The ring is of a distinctive nature to indicate to the called party that he is being called by a privileged party.

When the called party replies by removing his receiver, he loops line, thereby operating relay TB. in known manner. The relay locks up over. its winding II) and contacts ti! and b2 extends the called line back to the feed relay D at contacts 1572 and 2 3. Contact tr5 opens but before relay B can release relay D operates to close a circuit for relay B over contact d3. Contacts d! and d2 connect ringing current over wire IE2, ring tripping relay F and the line exten ing over contacts 122 and f3, 54 and b5 to the callers instrument and the bell thereat is rung. Contact dt starts a tone producing circuit and contact connects the tone source to a third winding of relay D. This tone is induced by means of the other windings of relay D into the called line to indicate to the called party that he is to await the removal of the receiver by the caller.

When the caller removes his receiver, relay F operates over the loop and locks up over its second winding, contacts fl, 2578 and b2 and at contacts f2 and f3 switches the calling'line through to the feed relay A. Contacts 1'5 and f8 open in the tone circuits and contact fl opens in the circuit for relay B. Relay A operates and at contact 113 maintains the circuit for relay B before that relay can release. It may here be noted that if the caller should remove his receiver before the called party, relay A will operate over back contacts (1! and (Z2 and will operate relay F by means of its winding (II) over contact a2. Thereafter when the called party removes his receiver, the ringing circuit over wire 1R2 will be found open and the caller is saved from receiving ringing current with the receiver to his ear. Besides the two feed relays and the two ring tripping relays relays B, H, TA and TB remain operated.

The first party to clear initiates the release of relay B by the opening of either contact d3 01' at. When relay B releases, relays F, TR and H release and the callers line is re-ccnn'ectcd to the line circuit of the P. A. X system, contact 223 connecting the cut-off relay K to the test wire in the multiple. Release of relay H extinguishes lamp If when the called partys line is tested it is found busy, relay H will not operate and relay BL will operate over contacts b1, i123 and $1 and the winding of relay BD following the release of relay S. Relay BD will not operate in this circuit. Contact bll disconnects the busy earth from the test wire in the multiple and connects cut-off relay K thereto to enable an incoming call to be made, contacts N2 and M3 reverse the battery connections to the indicator lamps so that lamp BL is now lit over rectifier MRA, battery being connected over relay RW but this relay will not operate in the lamp circuit. Contact 1714 opens the ringing circuit for the called party. The circuit may remain in this condition until the called line becomes free.

During this time however, incoming calls may be received as the test Wire of the privileged subscribers line is connected to battery over relay K, If an incoming call is received, relay K is operated and at contacts kl and k2 conects the speaking wires in the multiple over front contacts 174 and b5 to the privileged subscribers line disconnecting this line from the direct access path. Contact k3 opens to prevent operation of relay H should the directly called line become free during the continuance of the incoming call. Contact k l open to guard against irregular operation of relay BD or release of relay BL by short circuit. When the incoming call is terminated relay K releases and restores the operating circuit for relay H and, if in the meantime the directly called line has become free, relay H operates, releases relay BL by opening its holding circuit and short circuiting the relayat contact h5. During the release of relay BL the calling line is guarded by earth over contacts hl, bll, b3 and M2. The ensuing operations take place in the same manner a described earlier in connection with the line being found free when first tested. Lamp BL is extinguished and lamp GL is lit.

Instead of letting the connection remain in being until the wanted partys line becomes free, the caller may elect to follow one of three other courses. He may abandon the call by pressing the cancel key CK thereby operating relays W, X, Y and BD. Contacts 2 of these marking relays close a circuit for relay CO which holds over contacts col and b6 until relay B has released, the circuit for the latter relay having been opened at contact 001. Contact 002 opens the locking circuit of the marking relays and of relay BD so that release of the connection follows release of relay B, the opening of contact b6 finally releasing relay CO.

Instead of abandoning the connection in the manner described the caller may make another call. To do this he has merely to press the key apropriate to the line to be called whereupon relay ED is operated, the earth being applied over contact D12 and rectifier MRD. Relay BL is shunted by the earth over the marking key and releases and since contact tb2 is in its front position operation of relay BD releases relay B at contact bdl. As soon as relay B has released, relays TA and TB release and the circuit for relay B is made anew. Operations then proceed in the manner described for setting up a direct call, the caller removing his receiver after he has received a ring denoting that the called party has removed his receiver.

The third course is for the caller to exercise his right of way privilege. To do this he presses key RWK extending earth over contacts D12 and 1213 to relay RW. The relay operates and locks over contacts rwl and b2. Contact rw2 closes an operating circuit for winding (II) of relay F and contact 1103 a similar circuit for relay TR. Both relays operate and by the closure of contacts f4 and tr close a circuit for relay H over its lower winding. The speaking Wires are now extended and relays A and D operate, enabling the caller to announce himself and request clearance of the existing connection. The connection then remains held in the normal Way. Operation of relay H release relay BL and relay RW remains operated.

We claim:

1. In a telephone system, a calling station, a

called station, means at said calling station operated manually by the calling subscriber while the switchhook at that station remains in its normal position, means controlled by said operation for extending a connection to said called station, said connection including an incomplete speech transmission path from said calling station to said called station, and means thereafter controlled by operation of the switchhooks at the calling and called stations for completing said speech transmission path. 2. In a telephone system as claimed in claim 1, means for at times controlling said last means independently of said switchhooks, thereby to complete said speech transmission path.

3. In a telephone system, a calling station, a called station, means at said calling station operated manually by the calling subscriber while the switchhook at that station remains in its normal position, means controlled by said operation for extending a connection to said called station, said connection including an incomplete speech transmission path from said callin station to said called station, means thereafter controlled by the operation of the switchhook at said calling station for completing said speech transmission path at one point, and means con- Y trolled by the operation of the switchhook at said called station for completing said speech transmission path at another point.

4. In a telephone system, a subscribers line having a ringer normally connected thereto, subscriber controlled means for initiating a call from said line without disconnecting said ringer, means for extending said call to the line of another subscriber and signalling said other subscriber, and means operated responsive to said other subscriber answering for automatically applying ringing current to said calling line to operate said ringer.

' 5. In a telephone system, a calling line, a busy called line, switching apparatus operated to prepare a connection from said calling line to said called line before said called line becomes free, means in said apparatus thereafter operated automatically responsive to said called line becoming free for imprwsing ringing currentupon said called line to signal the called subscriber, and means operated responsive to said called subscriber answering for impressing ringing current upon said calling line to signal the calling subscriber.

6. In a system as claimed in claim 5, means controlled by said last-mentioned means for impressing a distinctive signal upon said called line during the period that said calling subscriber is being signalled.

7. In a telephone system, a calling line, a busy called line, switching apparatus operated to pre pare a connection from said calling line to said called line before -said called line becomes free, means in said apparatus thereafter operated automatically responsive to said called line becoming free for impressing ringing current upon said called line to signal the called subscriber, means operated responsive to said called subscriber answering for impressing ringing current upon said calling line to signal the calling subscriber, and means operated responsive to said calling subscriber answering for causing said last means to stop impressing said ringing current upon said calling line.

8. In a telephone system, a calling line, a busy called line, switching apparatus operated to prepare a connection from said calling line to said called line before said called line becomes free, means in said apparatus thereafter normally operated responsive to said called line becoming free for seizing said called line preparatory to Completing a. call thereto over said connection, and other switching apparatus operated at times while said connection to said called line remains prepared prior to said called line becoming free for extending a call to said calling line.

9. In a telephone system, a calling line, a busy called line, switching apparatus operated to prepare a connection from said calling line to said called line before said called line becomes free, means in said apparatus thereafter normally operated responsive to said called line becoming free for seizing said called line preparatory to completing a call thereto over said connection, and other switching apparatus operated at times while said connection to said called line remains prepared prior to said called line becoming free for extending a call to said calling line, and means controlled by said last call for preventing said first means'from seizing said called line at any time during said last call.

16. In a telephone system, a calling line, a busy called line, switching apparatus operated to prepare a connection from said calling line to said called line before said called line becomes free, means in said apparatus thereafter normally operated responsive to said called line becoming free for signalling the called subscriber over said called line, and other switching apparatus perated at times while said connection to said called line remains prepared prior to said called line becoming free for extending acall to said calling line.

ll. In a telephone system, a calling line, a busy called line, switching apparatus operated to prepare a connection from said calling line to said called line before said called line becomes free, means in said apparatus thereafter normally operated responsive to said called line becoming free for signalling the called subscriber over said called line, other switching apparatus operated at times while said connection to said called line remains prepared prior to said called line becoming free for extending a call to said calling line, and means controlled by said last call for preventing said first means from signalling said called subscriber at any time during said last call.

12. In a telephone system, a calling line, a busy called line, switching apparatus'operated to prepare a connection from said calling line to said called line before said called line becomes free, means in said apparatus thereafter normally operated responsive to said called line becoming free for seizing said called line preparatory to completing a call thereto over said connection, other switching apparatus operated at times while said connection to said called line remains prepared prior to said called line becoming free for extending a call to said calling line, and means independent of said first apparatus operated at times to seize said called line in the event that same becomes free before the termination of said last call.

13. In a telephone system, two subscribers lines, other subscribers lines, switching equipment operated to prepare a connection between the lines of said two subscribers at a time when one of said two subscribers is engaged in a call with one of said other subscribers, means for engaging either of said two subscribers in a new call at. any time while said connection remains prepared if, at the time of such new call, the other of said two subscribers is already engaged in a call, and means in said switching equipment operated responsive to either of said two subscribers lines becoming free if, at that time, the other one of said two subscribers lines is already free for seizing the lines of both of said two subscribers preparatory to completing a call therebetween over said connection.

14. In a telephone system, two subscribers lines, other subscribers lines, switching equipment operated to prepare a connection between the lines of said two subscribers at a time when one of said two subscribers is engaged in a call with one of said other subscribers, means for engaging either of said two subscribers in a new call at any time while said connection remains prepared if, at the time of such new call, the other of said two subscribers is already engaged in a call, and means in said switching equipment operated responsive to either of said two subscribers lines becoming free if, at that time, the other one of said two subscribers lines is already free for signalling one of said two subscribers.

15. In a telephone system, two subscribers lines, other subscribers lines, switching equipment operated to prepare a connection between the lines of said two subscribers at a time when one of said two subscribers is engaged in a call with one of said other subscribers, means for involving either of said two subscribers in a new call with one of said other subscribers While said connection remains prepared if, at the time of such new call, the other of said two subscribers is already engaged in a call, and means for preventing either of said two subscribers from being involved in a new call with one of said other subscribers at any other time while said connection is prepared.

16. In a telephone system, two subscribers lines, a device associated with both of said lines for an interval of time, means for engaging either of said lines in calls which do not involve the other of said lines, said means effective to cause each of said lines to be engaged, at least once during said interval, in a call not involving the other of said lines, said device operated responsive to either of said lines becoming free during said interval if, at the time such line becomes free, the other one of said lines is already free, and means for preventing the operation of said device if, at the time either of said lines becomes free, the other one of said lines remains engaged.

1'7. In a telephone system, a calling station, a plurality of called stations, switching apparatus responsive to a single manual operation performed by the calling subscriber while the switchhook at the calling station remains in its normal position for preparing a connection from said callin station to any particular called station desired by the calling subscriber, means in said apparatus normally controlled thereafter by operation of the switchhooks at said calling station and said particular called station for completinsaid prepared connection, said switching apparatus responsive to another single manual operation performed by the calling subscriber at times before said operation of said switchho-oks for releasing said prepared connection and preparing another connection from said calling station to any other particular called station desired by the calling subscriber.

13. In a telephone system, a calling station, a plurality of called stations, a plurality of nonlocking keys at said calling station, each of said keys corresponding to a different one of said called stations, switching apparatus operated responsive to a transitory operation of any of said keys for preparing a connection from said calling station to the called station corresponding to said operated key, means in said apparatus thereafter normally operated to complete said connection, and said switching apparatus operated responsive to a transitory operation of any other one of said keys before completion of said prepared connection for releasing said prepared connection and preparing a connection from said calling line to the called line corresponding to said other key.

19. In a telephone system, a calling station, a plurality of called stations, switching apparatus selectively controlled by a single manual operation performed by the calling subscriber to extend a connection from said calling station to any desired one of said called stations, said switching apparatus thereafter selectively controlled by a subsequent single manual operation performed by the calling subscriber to release said first connection and extend a connection from said calling station to any other called station is free, and means responsive to v the called subscriber answering for signalling the calling subscriber independently of said visual signal.

DAVID ADAM CHRISTIAN. BERNARD ANTHONY HENSLER. 

